The present invention relates to a method of detecting an abnormality of a control unit and a control unit employing the method, and more particularly to an abnormality detecting method of a vehicular control unit employing a serial communication type EEPROM.
An anti-skid control apparatus for automatically controlling wheel slip or preventing sustained wheel lock on braking have been developed and been widely used to be highly reliable and safe. The control of such an anti-skid control apparatus is generally executed in such a manner to execute a control program stored in a memory of a control unit. An EEPROM functioning as an external data memory is provided to the control unit and stores various information such as to problems of the anti-skid control apparatus. A microcomputer (CPU) of the control unit reads the data of the EEPROM at the time of the start up of the anti-skid control apparatus and informs the problems to vehicular occupants if such problem exist.
A Japanese Patent Provisional Publication No. 2-310642 discloses an apparatus for preventing a hang-up of a control system caused by a problem of the EEPROM which problem invites the disability to execute a writing process of data from the control unit to the EEPROM. This conventional control apparatus is provided with an EEPROM having a R/B terminal for outputting a write terminating signal to a CPU at the end of the writing processing and the CPU having a time monitoring means for monitoring a time period until the write terminating signal is transmitted to the CPU. The CPU is arranged to terminate the writing process according to the monitored time period even if the write terminating signal is not outputted.
However, the CPU of the conventional apparatus can not detect the abnormality In a reading process of data from the EEPROM to the CPU although it can detect the abnormality in the writing process. Therefore, this conventional apparatus has yet been insufficient at the point of the abnormality detection.